Such processes and circuits are advantageously used in message-transmitting equipment and/or in measuring equipment. In such equipment, in addition to each desired signal, at least one sinusoidal interference signal of known frequency is present whose parameter values, i.e. the values of Fourier coefficients or the amplitude and/or phase, are unknown. Thus, it is often desirable to determine such parameters at least by estimation.
The above-mentioned measuring devices are preferably electricity meters and are then used to measure an electric energy or are power measuring devices serving to measure an electric power. Depending on the design variant, values of an electrical active energy and/or of an electrical reactive energy and/or of an electrical apparent energy or values of an electrical active power and/or of an electrical reactive power and/or of an electrical apparent power may be determined by means of the process and/or circuit according to the present invention. Because harmonic signals of a network frequency signal are as a rule also present in an electric utility network in addition to a network frequency signal which has a frequency of 50 Hz or 60 Hz, an appertaining a.c. electricity meter or appertaining a.c. power-measuring device determines not only the energy or power of the network frequency signal but also that of the harmonic signals. In that case, the electricity meter and the power-measuring device each contains a signal designated hereinafter for the sake of simplification as the measuring signal to be evaluated which is equal to the sum of energies or powers of the network frequency signal and of the harmonic signals whose share can be determined at least in part by means of the process according to the instant invention and/or circuit according to the present invention.
In the above-mentioned measuring device it is however also possible to determine, additionally or solely, effective values of currents and/or electric voltages of the network frequency signal and of the harmonic signals by means of the process according to the instant invention and/or circuit according to the instant invention.
The above-mentioned message-transmitting devices are preferably ripple control installations in which information is known to be transmitted over an electric energy utility network by means of a modulated sinusoidal carrier signal. The transmitted information signal is distorted in the electric energy utility network by the network frequency signal of said electric energy utility network at a frequency of 50 Hz or 60 Hz as well as generally also by noise and other signals of a centralized ripple control system. The inventive method and circuit serve for the detection of transmitted ripple control signals. In a ripple control system receiver, the emitted and the transmitted modulated sinusoidal information signal of a ripple control system must then be determined from a measuring signal comprising the sum of the information signal, the sinusoidal network frequency signal, a plurality of sinusoidal harmonic signals of the network frequency signal, the noise and modulated sinusoidal carrier signals of other ripple control system signals all the latter of which are superimposed by addition in form of interference signals on the information signal. The frequencies of the sinusoidal interference signals and of the carrier signal of the information signal are known in advance, while the amplitude and/or phase of the information signal as well as the amplitudes and/or phases of all or part of the interference signal can be determined by means of the process according to the invention and/or the circuit according to the invention.
The process according to the invention and/or the circuit according to the invention can however also be used to determine at the same time signals of ripple control systems and an electrical active and/or reactive and/or apparent power or energy. In all application examples the values of the amplitudes and phases of the sinusoidal signals as well as of a frequently present d.c. voltage component are as a rule a function of time t.
A process of the type mentioned is known from the publication "Signal Processing IV, Theory and Applications, EUSIPCO 88, Grenoble, France, EURASIP, North Holland, A recursive estimator for the determination of unknown constant or slowly varying Fourier coefficients, P. Gruber, J. Toedtli, pages 1433 to 1436". In the process described therein, a sinusoidal signal of known frequency, the amplitude and/or phase of which varies in time, and which is an additive portion of a measuring signal, can be determined in real time, at least by estimation.
It is the object of the instant invention to improve and/or expand the known process significantly so that at least an additional sinusoidal signal of known frequency in the measuring signal, the amplitude and/or phase of which may vary in time, can be determined at least by estimation. This has the advantage, among others, that the values of the amplitudes and/or phases of the sinusoidal signals to be determined as well as the values of a d.c. voltage component to be determined are as a rule more precise.
Because the process according to the instant invention is also able to determine parameters of all the other sinusoidal signals present, at least by estimation, the advantage is especially great in those applications in which more than one sinusoidal signal is to be identified, e.g. a sinusoidal information signal and a sinusoidal interference signal or two sinusoidal interference signals.
Once it is known that a measuring signal comprises M sinusoidal signals all of which have a known, constant and different frequency, and in the case that the possibly varying amplitudes and phases of a plurality of these M sinusoidal signals are to be determined at least by estimation, the process and circuit according to invention supplies more precise values with little additional cost than the process known in the present state of the art if the latter were to be applied separately to each one of the plurality of sinusoidal signals.